The chemistry of gold (Au) surfaces and Au nanoparticles has been the focus of intense study, but recent synthetic advances have introduced a new class of “small” ligand-protected Au clusters with unique chemical and electronic properties. Ousters smaller than ˜2 nanometers (nm) in diameter differ from larger nanoparticles because their energy levels become quantized and they develop molecule-like electronic structures. Crystallographic efforts have confirmed that such small Au clusters form into atomically precise structures, and that some species, such as ligand-protected Au25 clusters, possess an inherent anionic (negative) charge. Ligand-protected Au25 clusters are a unique platform to study catalytic reactions because they bridge the size gap between molecules and larger nanoparticles, they possess an anionic charge, and their surface structure is precisely known. Despite these features, the catalytic activity of Au25 and similar atomically precise clusters have only been investigated experimentally for a handful of reactions, such as the oxidation of styrene and cyclohexane, the hydrogenation of aldehydes and ketones, and the electrochemical reduction of O2. One particularly appealing catalytic challenge to consider for the negatively charged Au25 cluster is the reduction of carbon dioxide. Not only is CO2 an important greenhouse gas, but it also represents an abundant starting material for the generation of fine chemicals and fuels.
These and other objects, aspects, and advantages of the present disclosure will become better understood with reference to the accompanying description and claims.